Quantity of users is social proof (more accurately, social evidence) of quality. The claim "we have high quality" is cheap: anyone can make it, and it's subjective enough that it can't be disproven in any absolute sense. But if you lie about having billions of users, you can be called out on that pretty easily; and if you say it honestly, it implies that billions of people like the quality of your product or service enough to use it. Billions of people can be wrong, but saying you have billions of users is still much better evidence of quality than saying you have quality.
So you’re arguing that popularity is a proxy for quality? So astrology is correct? There’s endless examples of popular things that are nonsense.
Of course the opposite is not true. Things are not bad because they are popular. I just don’t think there is any inherent correlation at all. Popularity generally measures memetic power and that’s it. Cold viruses are also popular.
